In recent years, Picture Archiving and Communications Systems (PACS) for diagnostic radiology have begun to be developed by a number of companies which hold the belief that in the near future much more of radiology's traditional work will be done electronically. Unfortunately, many of the basic questions about the clinical relevance of these undertakings have not been addressed in adequate detail. The application of ROC analysis to the problems involved in the development and operations of the systems clearly can help to answer a number of these questions. It is the purpose of this project to address some of these important issues through a comprehensive multi-observer study in which we will evaluate the requirements of diagnostic systems as these are related to picture archiving and communications. Specifically, we propose to investigate the digital acquisition and display requirements for primary diagnosis of chest images, an area of great importance if PACS is to succeed in the radiology environment. This project will utilize normal and abnormal chest images acquired with a unique high-resolution, high contrast sensitivity storage phosphor system. In the diagnostic accuracy study we will investigate requirements for acquisition and display matrices as well as the effects of physical characteristics (e.g., S/N, NEQ) and image processing on primary diagnosis of nodules, pneumothoraces, and interstitial disease.